Touch sensing systems (“touch systems”) are in widespread use in a variety of applications. Typically, the touch systems are actuated by a touch object such as a finger or stylus, either in direct contact, or through proximity (i.e. without contact), with a touch surface. Touch systems are for example used as touch pads of laptop computers, in control panels, and as overlays to displays on e.g. hand held devices, such as mobile telephones. A touch panel that is overlaid on or integrated in a display is also denoted a “touch screen”. Many other applications are known in the art.
To an increasing extent, touch systems are designed to be able to detect two or more touches simultaneously, this capability often being referred to as “multi-touch” in the art.
There are numerous known techniques for providing multi-touch sensitivity, e.g. by using cameras to capture light scattered off the point(s) of touch on a touch panel, or by incorporating resistive wire grids, capacitive sensors, strain gauges, etc into a touch panel.
WO2011/028169 and WO2011/049512 disclose multi-touch systems that are based on frustrated total internal reflection (FTIR). Light sheets are coupled into a panel to propagate inside the panel by total internal reflection (TIR). When an object comes into contact with a touch surface of the panel, the propagating light is attenuated at the point of touch. The transmitted light is measured at a plurality of outcoupling points by one or more light sensors. The signals from the light sensors are processed for input into an image reconstruction algorithm that generates a 2D representation of interaction across the touch surface. This enables repeated determination of current position/size/shape of touches in the 2D representation while one or more users interact with the touch surface. Examples of such touch systems are found in U.S. Pat. No. 3,673,327, U.S. Pat. No. 4,254,333, U.S. Pat. No. 6,972,753, US2004/0252091, US2006/0114237, US2007/0075648, WO2009/048365, US2009/0153519, WO2010/006882, WO2010/064983, and WO2010/134865.
The touch sensing technology gives the possibility to exchange hardware input devices with virtual equivalents. From US-2011/0285636-A1 it is known to have a virtual joystick, where a visual representation of a joystick is displayed on a touch screen. Touch data from the touch screen is processed to determine when the touch data indicates user interaction with the virtual joystick. Joystick data is generated based on the user interaction and the display of at least one other element on the touch screen can be adjusted based on the joystick data. Thus, a user may control movement of an element by positioning a finger in relation to the virtual representation of the joystick.
In touch systems in general, there is a desire to not only determine the location of the touching objects, but also to estimate the amount of force by which the touching object is applied to the touch surface. This estimated quantity is often referred to as “pressure”, although it typically is a force. Examples of touch force estimation in connection to a FTIR based touch-sensing apparatus is disclosed in the Swedish application SE-1251014-5. An increased pressure is here detected by an increased contact, on a microscopic scale, between a touching object and a touch surface with increasing application force. This increased contact may lead to a better optical coupling between the transmissive panel and the touching object, causing an enhanced attenuation (frustration) of the propagating radiation at the location of the touching object.
The availability of force/pressure information opens up the possibility of creating an alternative virtual joystick for touch-based control of software applications, which takes advantage of the available force/pressure information.
The object of the invention is thus to provide a pressure based virtual joystick which enables control of a graphical interactive object presented on a GUI of a touch sensing device.